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Message-ID: <2518652e-4a81-4b71-a0bd-a078d511f7b2@vivo.com>
Date: Thu, 7 Aug 2025 17:12:16 +0800
From: Liao Yuanhong <liaoyuanhong@...o.com>
To: Chao Yu <chao@...nel.org>, Jaegeuk Kim <jaegeuk@...nel.org>
Cc: linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] f2fs: Add bggc_block_io to adjust the priority of
BG_GC when issuing IO
On 8/7/2025 4:38 PM, Chao Yu wrote:
> On 8/6/25 15:09, Liao Yuanhong wrote:
>> Currently, we have encountered some issues while testing ZUFS. In
>> situations near the storage limit (e.g., 50GB remaining), and after
>> simulating fragmentation by repeatedly writing and deleting data, we found
>> that application installation and startup tests conducted after idling for
>> a few minutes take significantly longer several times that of traditional
>> UFS. Tracing the operations revealed that the majority of I/Os were issued
>> by background GC, which blocks normal I/O operations.
>>
>> Under normal circumstances, ZUFS indeed requires more background GC and
>> employs a more aggressive GC strategy. However, I aim to find a way to
>> minimize the impact on regular I/O operations under these near-limit
>> conditions. To address this, I have introduced a bggc_block_io feature,
>> which controls the prioritization of background GC in the presence of I/Os.
>> This switch can be adjusted at the framework level to implement different
>> strategies. If set to ALL_IO_PRIOR, all background GC operations will be
>> skipped during active I/O issuance. The default option remains consistent
>> with the current strategy, ensuring no change in behavior.
>>
>> Signed-off-by: Liao Yuanhong <liaoyuanhong@...o.com>
>> ---
>> Changes in v2:
>> Non ZUFS can also be adjusted through this option.
>> ---
>> Documentation/ABI/testing/sysfs-fs-f2fs | 13 +++++++++++++
>> fs/f2fs/f2fs.h | 18 +++++++++++-------
>> fs/f2fs/super.c | 2 ++
>> fs/f2fs/sysfs.c | 9 +++++++++
>> 4 files changed, 35 insertions(+), 7 deletions(-)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
>> index bc0e7fefc39d..12fda11d4da5 100644
>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
>> @@ -883,3 +883,16 @@ Date: June 2025
>> Contact: "Daeho Jeong" <daehojeong@...gle.com>
>> Description: Control GC algorithm for boost GC. 0: cost benefit, 1: greedy
>> Default: 1
>> +
>> +What: /sys/fs/f2fs/<disk>/bggc_block_io
>> +Date: August 2025
>> +Contact: "Liao Yuanhong" <liaoyuanhong@...o.com>
>> +Description: Used to adjust the BG_GC priority when issuing IO, with a default value
>> + of 1.
> Default value is 2 if CONFIG_BLK_DEV_ZONED is off?
>
> Thanks,
Sorry, I missed updating the description. Is it more reasonable to set
the default value to 0 for versions that disable CONFIG_BLK_DEV_ZONED?
If so, I will submit a new version to correct the description and
initial value settings here. Thanks, Liao
>> +
>> + ================== =============================================
>> + value description
>> + bggc_block_io = 0 Prioritize background GC
>> + bggc_block_io = 1 Stop background GC only when issuing read I/O
>> + bggc_block_io = 2 Stop background GC when issuing I/O
>> + ================== =============================================
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 46be7560548c..fe41b733fbc2 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -155,6 +155,12 @@ enum blkzone_allocation_policy {
>> BLKZONE_ALLOC_PRIOR_CONV, /* Prioritize writing to conventional zones */
>> };
>>
>> +enum bggc_block_io_policy {
>> + BGGC_PRIOR,
>> + READ_IO_PRIOR,
>> + ALL_IO_PRIOR,
>> +};
>> +
>> /*
>> * An implementation of an rwsem that is explicitly unfair to readers. This
>> * prevents priority inversion when a low-priority reader acquires the read lock
>> @@ -1804,6 +1810,7 @@ struct f2fs_sb_info {
>> spinlock_t dev_lock; /* protect dirty_device */
>> bool aligned_blksize; /* all devices has the same logical blksize */
>> unsigned int first_seq_zone_segno; /* first segno in sequential zone */
>> + unsigned int bggc_block_io; /* For adjust the BG_GC priority when issuing IO */
>>
>> /* For write statistics */
>> u64 sectors_written_start;
>> @@ -2998,13 +3005,10 @@ static inline bool is_idle(struct f2fs_sb_info *sbi, int type)
>> if (sbi->gc_mode == GC_URGENT_HIGH)
>> return true;
>>
>> - if (zoned_gc) {
>> - if (is_inflight_read_io(sbi))
>> - return false;
>> - } else {
>> - if (is_inflight_io(sbi, type))
>> - return false;
>> - }
>> + if (sbi->bggc_block_io == READ_IO_PRIOR && is_inflight_read_io(sbi))
>> + return false;
>> + if (sbi->bggc_block_io == ALL_IO_PRIOR && is_inflight_io(sbi, type))
>> + return false;
>>
>> if (sbi->gc_mode == GC_URGENT_MID)
>> return true;
>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>> index e16c4e2830c2..a21cecc5424e 100644
>> --- a/fs/f2fs/super.c
>> +++ b/fs/f2fs/super.c
>> @@ -4629,9 +4629,11 @@ static int f2fs_scan_devices(struct f2fs_sb_info *sbi)
>>
>> logical_blksize = bdev_logical_block_size(sbi->sb->s_bdev);
>> sbi->aligned_blksize = true;
>> + sbi->bggc_block_io = ALL_IO_PRIOR;
>> #ifdef CONFIG_BLK_DEV_ZONED
>> sbi->max_open_zones = UINT_MAX;
>> sbi->blkzone_alloc_policy = BLKZONE_ALLOC_PRIOR_SEQ;
>> + sbi->bggc_block_io = READ_IO_PRIOR;
>> #endif
>>
>> for (i = 0; i < max_devices; i++) {
>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>> index f736052dea50..efea15209788 100644
>> --- a/fs/f2fs/sysfs.c
>> +++ b/fs/f2fs/sysfs.c
>> @@ -674,6 +674,13 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
>> sbi->blkzone_alloc_policy = t;
>> return count;
>> }
>> +
>> + if (!strcmp(a->attr.name, "bggc_block_io")) {
>> + if (t < BGGC_PRIOR || t > ALL_IO_PRIOR)
>> + return -EINVAL;
>> + sbi->bggc_block_io = t;
>> + return count;
>> + }
>> #endif
>>
>> #ifdef CONFIG_F2FS_FS_COMPRESSION
>> @@ -1172,6 +1179,7 @@ F2FS_SBI_GENERAL_RW_ATTR(max_read_extent_count);
>> #ifdef CONFIG_BLK_DEV_ZONED
>> F2FS_SBI_GENERAL_RO_ATTR(unusable_blocks_per_sec);
>> F2FS_SBI_GENERAL_RW_ATTR(blkzone_alloc_policy);
>> +F2FS_SBI_GENERAL_RW_ATTR(bggc_block_io);
>> #endif
>> F2FS_SBI_GENERAL_RW_ATTR(carve_out);
>> F2FS_SBI_GENERAL_RW_ATTR(reserved_pin_section);
>> @@ -1342,6 +1350,7 @@ static struct attribute *f2fs_attrs[] = {
>> #ifdef CONFIG_BLK_DEV_ZONED
>> ATTR_LIST(unusable_blocks_per_sec),
>> ATTR_LIST(blkzone_alloc_policy),
>> + ATTR_LIST(bggc_block_io),
>> #endif
>> #ifdef CONFIG_F2FS_FS_COMPRESSION
>> ATTR_LIST(compr_written_block),
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